Scribing method for brittle materials, a cutter wheel used therefor and an apparatus provided therewith

ABSTRACT

It is possible by use of a disclosed cutter wheel to obtain deep vertical cracks inside brittle materials while suppressing generation of horizontal cracks. Such a cutter wheel for brittle materials comprises a disk with two side planes and an outer periphery between them, outer periphery comprising two bevel portions and a ridge portion between them. The ridge portion comprises a plurality of peaks aligned along a circumferential line. For example, the ridge portion comprises a straight line connecting two adjacent peaks in the plurality of peaks. Alternatively, the ridge portion comprises a depression between two adjacent peaks in the plurality of peaks, and the depth of the depression is deeper than the straight line connecting between the two adjacent peaks. Preferably, the peaks are arranged at an equal distance between them.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a scribing method for forming scribe lines on a brittle plate such as a glass plate, a semiconductor wafer or a ceramic plate, a cutter wheel used for such a method by rotating on a brittle sheet, and an apparatus provided with such a cutter wheel.

[0003] 2. Description of Prior Art

[0004] A cutter wheel for brittle materials is fabricated by working a disk made of a cemented carbide alloy, sintered diamond or the like. The disk is ground at the outer periphery obliquely on the two sides to form an edge having a V-character-like shape. A rotational shaft is fixed to a shaft hole provided at the center of the disk, and the shaft is mounted rotatively in a manual cutter or in a cutter head of an automatic scriber or the like. Accordingly, the cutter wheel is rotated on a brittle plate such as a glass sheet, a semiconductor wafer or a ceramic plate under a pressure to form scribe lines thereon.

[0005] However, such a conventional cutter wheel cannot generate deep vertical cracks inside a brittle sheet. Further, it is liable to slip on a brittle sheet on scribing, and this abrades the edge. Residual stress is remained along scribe lines. Further, when the brittle sheet is cut along the scribe lines, unnecessary defects due to horizontal cracks are liable to be generated at the sections subjected to the cutting. This is a problem on the quality of brittle cutting.

[0006] Deep vertical cracks can be obtained by the cutter wheel disclosed in the U.S. Pat. No. 5,836,229 assigned to the same assignee of this application. As shown in FIG. 1, the cutter wheel 1 has a disk with V-character-like bevel portions 2, and an edge 3 between the bevel portions 2 having depressions 4 of microscopic sizes formed at an equal distance between them to provide protrusions 5 between them which contact a brittle sheet. It is possible by use of the cutter wheel 1 to generate deep vertical cracks into a brittle sheet. Further, the residual stress is decreased, and the generation of unnecessary defects due to horizontal cracks along the scribe lines is not increased.

[0007] One of main uses of the cutter wheel for brittle materials is cutting of glass sheets used for flat panel displays (FPD's for abbreviation) such as liquid crystal display (LCD for abbreviation) panels. Recently, there is a high demand for LCD panels of high quality. Therefore, it is required to suppress the generation of unnecessary horizontal cracks as much as possible.

SUMMARY OF THE INVENTION

[0008] An object of the present invention is to provide a scribing method for brittle materials which generates deep vertical cracks while more suppressing generation of horizontal cracks.

[0009] Another object of the present invention is to provide a cutter wheel for brittle materials which generates deep vertical cracks while suppressing generation of unnecessary horizontal cracks.

[0010] A further object of the present invention is to provide a scribing apparatus which suppresses generation of horizontal cracks by using the cutter wheel as a scribing means.

[0011] A cutter wheel for brittle materials in accordance with the present invention comprises a disk with two side planes and an outer periphery between them, the outer periphery provided with two bevel portions, and a ridge portion between them of a polygon. The ridge portion comprises a plurality of peaks aligned along a circumferential line. For each pair of two adjacent peaks in the plurality of peaks, the ridge portion except the peaks extends along or lower than a straight line connecting the two adjacent peaks. Preferably, the peaks are arranged at an equal distance between them. For example, for each pair of two adjacent peaks, the ridge portion is a polygon form with vertices along the straight line connecting the two adjacent peaks. Thus, the edge portion has a polygon shape. Alternatively, for each pair of two adjacent peaks, the ridge portion has a depression between the two adjacent peaks, and the depression extends lower than the straight line connecting the two adjacent peaks.

[0012] An advantage of the present invention is that generation of horizontal cracks is remarkably suppressed while generating deep vertical cracks.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] These and other objects and features of the present invention will become clear from the following description taken in conjunction with the preferred embodiments thereof with reference to the accompanying drawings, and in which:

[0014]FIG. 1 is a diagram for explaining a prior art cutter wheel;

[0015]FIG. 2 is a diagram of a cutter wheel of a first embodiment of the invention;

[0016]FIG. 3 is a diagram of a cutter wheel of a second embodiment of the invention;

[0017]FIG. 4 is a schematic front view of a machine for fabricating cutter wheels;

[0018]FIG. 5 is a diagram of a cutter wheel of a third embodiment of the invention;

[0019]FIG. 6 is a diagram of a cutter wheel of a fourth embodiment of the invention;

[0020]FIG. 7 is a schematic front view of an automatic scriber for brittle materials having a general mechanism;

[0021]FIG. 8 is a side view of the automatic scriber;

[0022]FIG. 9 is a partially broken front view of a manual cutter for brittle materials.

[0023]FIG. 10 is a schematic front view of a device using a cutter wheel; and

[0024]FIGS. 11A and 11B are schematic front views of other cutter wheels with shafts.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Referring now to the drawings, wherein similar reference numerals and characters designate similar or corresponding parts throughout the several views, FIG. 2 shows a cutter wheel 11 of a first embodiment of the invention. FIG. 2 includes a side view on the left side, a front view in the center and a cross sectional view on the right side. The cutter wheel 11 has a disk with two side planes made of a cemented carbide alloy and the outer periphery thereof. The outer periphery has two bevel portions 12 and a V-character-like ridge 13 between them. The ridge 13 has a peak in contact with a brittle sheet for forming scribe lines. The ridge 13 has a shape of a regular polygon of sixty vertices when observed from a side of the wheel. For simplicity in FIG. 2, the ridge 13 has a shape of a regular polygon of eighteen vertices. The two bevel portions 12 extending from a side of the polygon of the ridge 13 make an angle θ of 125° in a section perpendicular to the disk. Any section in the bevel portions 12, including the ridge 13, has a form of a regular polygon of sixty vertices. FIG. 2 shows on the right side a cross sectional view of a polygon corresponding to a cross section obtained after cutting the cutter wheel along Q-Q′ line in the front view situated in the center of FIG. 2. The cutter wheel 11 has a central hole for inserting a rotational shaft (not shown).

[0026] As will be explained below, the bevel portions 12 are formed by grinding, and this results in the above-mentioned ridge 13 having the form of the regular polygon of sixty vertices.

[0027]FIG. 3 shows a cutter wheel 11′ of a second embodiment in accordance with the present invention. FIG. 3 includes a side view of the cutter wheel 11′ on the left side, a front view of the same in the center and a cross sectional view thereof on the right side. The cross sectional view of a circle corresponds to the cross section obtained after cutting the cutter wheel 11′ along R-R′ line in the front view. The cutter wheel 11′ has a center hole for inserting a rotational shaft (not shown). The cutter wheel 11′ is obtained by working only the circular ridge of a normal cutter wheel to form a polygon shape at the ridge with many flat planes 15 and vertices 16 between them alternately along the ridge. The cutter wheel 11′ has sixty (for simplicity, eighteen in FIG. 3) flat planes 15 and vertices 16 alternately between them along the ridge.

[0028] The dimensions of the cutter wheel 11 (and 11′) are as follows. Wheel diameter: 2.5 mm. Wheel thickness: 0.65 mm. Edge angle (θ); 125°.

[0029] By using the cutter wheel 11 (and 11′), scribing is performed according to following scribing conditions. Edge load: 2.0 Kgf. Scribing speed: 300 mm/sec. Thickness of glass plate: 0.7 mm.

[0030] When the cutter wheel 11 (and 11′) is used according to the scribing data, the depth of vertical cracks is of the same order as that generated by the prior art cutter wheel 1 shown in FIG. 1, while the generation of horizontal cracks is suppressed more. As to the prior art cutter wheel shown in FIG. 1, it is understood that deep vertical cracks are generated due to impacts repeatedly generated many times when the protrusions 5 along the ridge strike the brittle plate at scribing. However, the protrusions 5 themselves are parts of a circumferential line which contacts the brittle plate, and it is further understood that portions 4 a and 4 b in FIG. 1 formed at the depressions 4 generate horizontal cracks. On the other hand, the generation of horizontal cracks is small for the cutter wheel 11 (and 11′) of the first (and second) embodiment, and the reason is assumed as follows. The cutter wheel 11 (and 11′) gives an impact to the brittle plate at each vertex (peak) of the regular polygon along the ridge, but the vertex itself does not have a length along the direction of the ridge. Further, because the ridge except the vertices consists of straight lines or sides of the regular polygon, the crack depth into the brittle plate by the linear portions becomes smaller. Thus, the generation of horizontal cracks is suppressed.

[0031]FIG. 4 shows a machine for fabricating the cutter wheel 11. A disk-like wheel 20 made of a cemented carbide alloy has a shaft (not shown) and the shaft is set rotatively. When a bevel plane is formed on the left side of the V-character-like ridge, the wheel 20 is fixed, and a grinder 22 is moved in a direction along the bevel plane to form a plane 23 including a side of the regular polygon with sixty vertices, and the plane 23 is ground. This is repeated each time the wheel 20 is rotated by 6° (=360/60), and sixty planes are formed on the left side of the V-character-like ridge. Thereafter, in order to form the other bevel planes on the right side, the wheel 20 is removed and reversed. Then, it is set again rotatively, and the position of the wheel 20 is determined according to working conditions by using an image processing system (not shown). Then, the grinder 22 is moved again similarly to form a plane 25 (represented by a dotted line) including a side of the regular polygon on the right side of the V-character-like ridge. This is repeated each time the wheel 20 is rotated by 6°. Thus, a cutter wheel 11 is obtained to have the edge with a shape of a polygon with sixty vertices.

[0032] It is also possible to produce the cutter wheel 11 by using a prior art cutter wheel provided with a circular V-shaped ridge at an outer periphery. The prior art wheel is worked by the machine shown in FIG. 4 to grind the bevel portions including the ridge portion as explained above. It is similarly possible to produce the cutter wheel 11′ by using a prior art cutter wheel having a circular V-shaped ridge at an outer periphery. The prior art cutter wheel is similarly worked by a machine disclosed in the U.S. Pat. No. 5,836,229 to grind only the ridge portion.

[0033] Alternatively, electro-discharge machining may be used to fabricate the cutter wheel 11, 11′ instead of grinding carried out by the above-mentioned machine.

[0034] In the first and second embodiments (FIGS. 2 and 3), as explained above, the ridge has a shape of a polygon when observed from a side of the cutter wheel. Therefore, an impact is given at each vertex of the polygon to a brittle plate thereby generating deep vertical cracks, while generation of unnecessary horizontal cracks is suppressed except the vertices. This results in that the generation of horizontal cracks can be decreased while vertical cracks are deeply generated inside the brittle materials.

[0035]FIG. 5 shows a cutter wheel 31 of a third embodiment of the invention. FIG. 5A is a side view of the cutter wheel 31 and FIG. 5B is a front view of the same. A depression 14 is formed along the ridge for each side of the regular polygon with 60 vertices, similarly to the depressions 4 of the prior art wheel shown in FIG. 1. The depressions 14 are formed to have a depth below a line or a side connecting adjacent two vertices of the regular polygon. For example, the depth of the depression 14 is about 0-20% of the length of the side of the regular polygon. Thus, the cutter wheel 31 does not have linear portions along the ridge. The depressions 14 may be formed by using a thin disk-like grinder moved in a direction perpendicular to the disk, as disclosed in the U.S. Pat. No. 5,836,229.

[0036]FIG. 6 shows a cutter wheel 31′ of a fourth embodiment of the invention. FIG. 6A is a side view of the cutter wheel 31′ and FIG. 6B is a front view of the same. The cutter wheel 31′ is provided with sixty vertices (edges) at the ridge (a polygon shape with eighteen vertices is shown in FIG. 6A for simplicity).

[0037] The cutter wheel 31′ is obtained by working the ridge of the cutter wheel 11′ in FIG. 3 with sixty flat planes 15 and vertices 16 along the ridge, and round bevel planes 12′ . The cutter wheel 31′ is obtained after forming depressions 14 between the vertices 16 along the ridge. The depressions 14 are formed to have a depth below a line or a side connecting adjacent two vertices of the regular polygon. For example, the depth of the depression 14 is about 0-20% of the length of the side of the regular polygon. Thus, the cutter wheel 31′ does not have linear portions along the ridge. The depressions 14 may be formed by using a thin disk-like grinder moved in a direction perpendicular to the disk, as disclosed in the U.S. Pat. No. 5,836,229.

[0038] In the above-mentioned ridge of the cutter wheel 11 or 11′ shown in FIG. 2 or 3, the linear portions are provided except the vertices of the polygon, and the generation of the horizontal cracks on the brittle plate is decreased. On the other hand, in the cutter wheel 31 or 31′ shown in FIG. 5 or 6, the depressions 14 are provided deeper than the linear portions in the cutter wheel 11 or 11′. Thus, the cutter wheel 31 in FIG. 5 (or 31′ in FIG. 6) is not in close contact with portions between the vertices resulting in that the generation of the horizontal cracks is suppressed more than the case of the cutter wheel with the linear lines 13 in FIG. 2 (or the flat planes 15 in FIG. 3).

[0039] The above-mentioned dimensions of the cutter wheels 11, 11′, 31, 31′ are exemplified data. Recommended dimensions of a general cutter wheel are given below. Wheel diameter: 1-20 mm. Wheel thickness: 0.6-5 mm. Edge angle (θ) 90-160°.

[0040] General scribing conditions are as follows. Edge load: 0.8-60 Kgf. Scribing speed: 50-1,000 mm/sec.

[0041] In the third or fourth embodiment, depressions are formed between the vertices, as explained above. Therefore, necessary vertical cracks can be obtained by a smaller scribing load impressed at the ridge, while the generation of horizontal cracks can be decreased more than the cutter wheel of the first or second embodiment.

[0042] The cutter wheel explained above is suitable for an automatic scriber and a manual cutter for brittle materials.

[0043]FIGS. 7 and 8 are a front view and a side view of a general automatic scriber for brittle materials. A table 41 for setting a brittle plate is rotated by a rotation table 42 in a horizontal plane, and it is moved along a rail 45 in Y direction (or left-to-right direction in FIG. 7) by a ball screw 44. On the other hand, a cutter head 46 is moved in X direction (or left-to-right direction in FIG. 8) along rails 47. The cutter head 46 has the cutter wheel 11, 11′, 31, or 31′ with a shaft fitted at the center thereof, and the shaft is supported rotatively at a lower end of the cutter head 46.

[0044] On scribing, each time the table 41 is moved in Y direction by a predetermined pitch, the cutter head 46 is moved in X direction. Thus, the brittle plate is scribed in X direction. Then, after the table 41 is rotated by 90°, scribing is performed similarly. Accordingly, the brittle plate is also scribed in Y direction.

[0045] The automatic scriber for brittle materials explained above is one example of a scriber. The cutter wheel of the invention can also be used in other types of scribers. For example, the cutter head 46 is fixed, and the table is moved in X and Y directions. Alternatively, the table 41 is fixed, and the cutter head 46 is moved in X and Y directions.

[0046]FIG. 9 shows the cutter wheel 11, 11′, 31, or 31′ mounted in a manual glass cutter disclosed in Japanese Utility Model Publication 62-23, 780/1987. The glass cutter has a cylindrical handle 61 for grip and a head 62 provided at a lower side thereof. The glass cutter wheel 11, 11′, 31, or 31′ with a shaft is mounted to the head rotatively around the shaft. Further, an oil chamber 63, a cap 64 thereof and a relevant mechanism 65-93 are provided in order to supply oil to the glass cutter wheel 11, 11′, 31, or 31′, but detailed explanation thereon is omitted here.

[0047]FIG. 10 shows the head 62 shown in FIG. 9. A shaft 11 a is inserted through the hole of the glass cutter wheel 11, 11′, 31, or 31′, and two ends of the shaft 11 a are supported at a two-fork type member of the head 62. A cap 62 a stops the shaft 11 a

[0048] The cutter wheel 11, 11′, 31, or 31′ is provided as an element as shown in FIGS. 2, 3, 5 and 6. When it is used, a shaft 11 a shown in FIG. 10 is inserted to the center hole provided in the wheel 11, 11′, 31, or 31′. However, because the outer diameter of the wheel is very small, the diameter of the shaft 11 a may become equal to or smaller than 1 mm, and it is difficult to handle the shaft. Therefore, as shown in FIG. 11A, a shaft 11 a′ may be integrated with the main body of the cutter wheel to form a single unit 11″. Alternatively, as shown in FIG. 11B, a pivot shaft 11 a″ may be integrated with the main body of the cutter wheel to form a single unit 11″. The shape of the shaft depends on the structure of the bearing at the cutter head 62.

[0049] In the above-mentioned embodiments of the invention, a cutter wheel has a shape of a regular polygon. However, a cutter wheel of a polygon in shape has a similar advantage.

[0050] Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims unless they depart therefrom. 

What is claimed is:
 1. A cutter wheel comprising: a disk having two side planes and an outer periphery between them, said outer periphery comprising two bevel portions; and a ridge portion between said two bevel portions; wherein said ridge portion comprises a plurality of peaks aligned along a circumferential line, and for each pair of two adjacent peaks in the plurality of peaks said ridge portion except the peaks extends along corresponding each one of straight lines connecting said two adjacent peaks.
 2. A cutter wheel according to claim 1, wherein said plurality of peaks are aligned to have an equal distance between them.
 3. A cutter wheel according to claim 1, wherein said ridge portion extends along the straight line connecting the two adjacent peaks.
 4. A cutter wheel according to claim 1, wherein for each pair of the two adjacent peaks in the plurality of peaks said ridge portion comprises a depression between the two adjacent peaks, the depression extending lower than the straight line connecting the two adjacent peaks.
 5. A cutter wheel according to claim 4, wherein a depth of said depression is 0 to 20% of a length of the straight line connecting the two adjacent peaks.
 6. A cutter wheel according to claim 1, wherein the number of the peaks is between 16 and
 300. 7. A cutter wheel according to claim 1, wherein said circumferential line has a diameter of between 1 to 20 mm.
 8. A cutter wheel according to claim 1, wherein said disk has a thickness of between 0.6 and 5 mm.
 9. A cutter wheel according to claim 1, wherein said two bevel portions make an angle of between 90 and 160 degrees in a section perpendicular to said two side planes.
 10. A cutter wheel according to claim 1, wherein said disk has a hole at the center thereof.
 11. A cutter wheel according to claim 1, wherein said disk with a hole at the center thereof, comprises a shaft fitted to said hole and integrated with said disk.
 12. A scriber for brittle materials comprising: a table on which a brittle plate is set; and a control means for moving a cutter head provided with a cutter wheel relative to said table in a position that said cutter wheel is in contact with said brittle plate; wherein said cutter wheel comprises a disk having two side planes and an outer periphery between them, the outer periphery comprises two bevel portions and a ridge portion between them, the ridge portion comprises a plurality of peaks aligned along a circumferential line, and for each pair of the two adjacent peaks in the plurality of peaks the ridge portion except the peaks extends along or lower than a straight line connecting the two adjacent peaks.
 13. A scriber for brittle materials comprising: a grip having a holder at an end thereof; and a cutter wheel supported rotatively by said holder; wherein said cutter wheel comprises a disk having two side planes and an outer periphery between them, said outer periphery comprises two bevel portions and a ridge portion between them, said ridge portion comprises a plurality of peaks aligned along a circumferential line, and for each pair of the two adjacent peaks in the plurality of peaks the ridge portion except the peaks extends along or lower than a straight line connecting the two adjacent peaks. 